Adhesive for application of functional articles to the skin and comfortable removal

ABSTRACT

The present invention relates to topical adhesives used for the attachment of articles to the skin. The topical adhesive provides secure attachment and is pleasing to the skin upon application, yet causes no discomfort and a low level of adhesive residue on the skin upon removal. The topical adhesive is selected to have rheological characteristics determined by the relationship between the elastic modulus G′ and the viscous modulus G″.

FIELD OF THE INVENTION

The present invention relates to topical adhesives for attachment to theskin. In particular the present invention relates to such topicaladhesives which can be employed for application of functional articlesto the skin, particularly for the adhesion of functional articles or theimprovement of the function of such articles. Functional articles inthis context are cosmetic or pharmaceutical delivery articles whichprovide a substance to the skin such as skin treatment substances,creams, lotions, hormones, vitamins, deodorants, or drugs; alternativelycosmetic or pharmaceutical delivery articles can also provide asubstance to emanate away from the skin such as insecticides, inhalationdrugs, or perfumes; further the adhesive of the present invention canalso be used in functional articles which are not attached to the skinbut as a component in articles which require a high residence time onthe skin such as decorative cosmetics (lipstick, eye colors, stagemake-up) or cleaning article (hand cleaner, face mask, hygienic cleanserespecially for pores). The topical adhesive provides secure attachmentor increased residence time and is pleasing to the skin uponapplication, yet causes no discomfort and a low level of adhesiveresidues on the skin upon removal. This is achieved by selecting thechemical composition and rheological characteristics of the topicaladhesives, in particular with reference to the relationship between theelastic modulus G′ and the viscous modulus G″ of the topical adhesive.

BACKGROUND OF THE INVENTION

The general prior art in the field of topical adhesives for attachmentto the skin is particularly developed in the field of band-aids,plasters and bandages. These articles are, however, typically applied inan emergency situation where for example a cut into the skin of thewearer has occurred and absorption of the body liquids emanating from awound is desired. In this context performance aspects of the absorbentarticle such as comfortable and easy use and application, painlessremoval, discreteness are subordinate to criteria such as sterility,healing support, mechanical protection of the wound. Also such woundcovering absorbent articles are mostly adhered to skin areas where priorto application of the absorbent article body hair can be removed orwhere little or no hair grows.

The present invention relates to topical adhesives which areparticularly useful to functional articles such as cosmetic orpharmaceutical delivery articles which provide a substance to the skinsuch as skin treatment substances, creams, lotions, hormones, vitamins,deodorants, or drugs; alternatively cosmetic or pharmaceutical deliveryarticles can also provide a substance to emanate away from the skin suchas insecticides, inhalation drugs, or perfumes; further the adhesive ofthe present invention can also be used in functional articles which arenot attached to the skin but as a component in articles which require ahigh residence time on the skin such as decorative cosmetics (lipstick,eye colors, stage make-up) or cleaning article (hand cleaner, face mask,hygienic cleanser especially for pores). Such articles are not used forabsorption of body liquids. For example attachment of a vitamin plasterto the skin or of an inhalation drug releasing article to the breast cansuitably be done by the adhesive of the present invention. Inclusion ofthe adhesive into decorative cosmetics allows to increase theirresistance to wearing off while not creating a removal problem.

Topical adhesives that are used for absorbent articles such as sanitarynapkins and pantiliners have generally been disclosed in US statutoryinvention registration H1602 or WO 96/33683. Some more details of theadhesive have been disclosed in PCT application WO 95/16424. In thisdocument sanitary articles having a topical adhesive which is applied onthe wearer facing side of a sanitary napkin along the entire peripheryare disclosed. The problem underlying this document is primarily thesafe attachment to the skin but mentions also the problems of detachmentof such articles after use without causing undue pain to a wearer.

The disclosure of WO 95/16424 includes a detailed analysis of thecriteria for the topical adhesive in respect to rheological criteria.However, this document has little regard to the problem of painlessremoval of such articles since the rheological criteria taught includeepilatory, i.e. hair removal, compositions which are commerciallyavailable such as STREP MIELE (™) sold in Italy by Laboratori Vaj S.p.A.The adhesives for topical attachment mentioned in WO 95/16424 includealso today's pressure sensitive adhesives which are used to attachsanitary napkins to undergarments. Further, this document onlyidentifies static Theological characteristics but is silent as to thedynamic rheological behaviour of a topical adhesive.

In WO 96/13238 a frequency dependent topical adhesive model isdisclosed. However, all measurements disclosed, e.g. on page 9, weremade at temperatures between −60° C. and +120° C. and at actualfrequencies of 0.1 to 100 rad/s. In order to obtain the necessary dataat application temperature (about 20° C., typical bath room, i.e.storage temperature) the Williams-Landel-Ferry (hereinafter WLF)equation was used.

This WLF equation is empirical and only valid within certain limits e.g.it cannot be used to extrapolate to temperatures below the glasstransition temperature of a polymeric adhesive also the WLF cannot beused on the basis of values obtained below the glass transitiontemperature. Details about the WLF equation and its applicability can befound in “Principles of Polymer processing” by Z. Tadmor and C. G.Gogos, published by John Wiley & Sons or in “Viscoelastic Properties ofPolymers” by J. D. Ferry also published by John Wiley & Son. Since thisis already missing from WO 96/13238 the applicability of the discloseddata cannot be assessed.

European Patent Application EP-638 303 discloses the use of a topicaladhesive on side cuffs of sanitary napkins in order to keep the cuffs inan upright position. Swiss publication CH-643730 discloses the use of avery long sanitary napkin having chamfered outer edges with a topicaladhesive at the four corners of the outer edges in order to provide atopical adhesive area well outside the region of pubic hair growth. Bothapplications are silent as to the adhesive composition.

Based on the above state of the art it is an objective of the presentinvention to provide a topical adhesive for secure attachment andpainless removal from the skin for functional articles, combined with areduced amount of residual adhesive that remains on the skin or on thehairs after removal of the topical adhesive composition.

It is yet a further objective of the present invention that the adhesivefor topical attachment does not cause a cold or otherwise unacceptabletemperature sensation upon application despite a temperature differenceof the adhesive in respect to the skin temperature.

In addition to the above objectives of the present invention it is alsodesirable for topical adhesives to provide additional benefits such asphysical protection. Further, topical adhesives which do not affect thenatural skin condition, e.g. by being breathable or water vapourtransmitting are preferred.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is useful to attach functional articles to theskin or improve the function of such articles when worn on the skin.Functional articles are cosmetic or pharmaceutical delivery articleswhich provide a substance to the skin such as skin treatment substances,creams, lotions, hormones, vitamins, deodorants, or drugs; alternativelycosmetic or pharmaceutical delivery articles can also provide asubstance to emanate away from the skin such as insecticides, inhalationdrugs, or perfumes; further the adhesive of the present invention canalso be used in functional articles which are not attached to the skinbut as a component in articles which require a high residence timeon-the skin such as decorative cosmetics (lipstick, eye colors, stagemake-up) or cleaning article (hand cleaner, face mask, hygienic cleanserespecially for pores). Such articles are non-absorbent for bodilyliquids. The article typically has a wearer facing surface and anoutside surface. The topical adhesive allows secure attachment of anarticle to the skin of the wearer and supports the functionality of thearticles. The term “functional” in this context means that the articleafter being placed on the skin fulfills an additional function which issupported or improved by the topical adhesives according to the presentinvention.

Detailed analysis of the sequence of common situations occurring fromthe application of a functional article to the time of removal of suchan article has shown that specific adhesive characteristics need to besatisfied in order to achieve the desired performance objectives tosupport the function of the articles, in particular secure initialattachment, secure attachment during use, painless removal at the endand a reduced level of adhesive residues on the skin after removal. Thecharacteristics which have been considered in this context are theelastic modulus describing the elastic behaviour of the material and theviscous modulus which describes the viscous behaviour of the adhesivematerial.

The viscous behaviour of the adhesive can be interpreted to represent anindication of the ability of the adhesive to quickly attach and securelyadhere. The elastic behaviour can be interpreted as an indication of the“hardness” behaviour of the adhesive. Its value is also critical forgood initial attachment. Their combination is believed to be anindicator of the required force upon removal. The relation betweenelastic and viscous modulus is considered to be an indication on whichfraction of the removal energy will be dissipated within the adhesiveand which fraction is available to trigger the actual removal. Therelation between the elastic and viscous modulus also gives anindication of the internal cohesiveness of the adhesive, which is inturn related to the possible presence of adhesive residues on the skinafter removal of the topical adhesive composition.

In order to provide topical adhesives for functional articles therelation between the elastic modulus and the viscous modulus as well astheir dynamic behaviour is of key importance.

The topical adhesive has an elastic modulus at a temperature of 37° C.(100° Fahrenheit) abbreviated G′₃₇ and a viscous modulus at atemperature of 37° C. (100° Fahrenheit) of G″₃₇. The differenceΔ(G′₃₇−G″₃₇) between the elastic modulus G′₃₇ at a frequency of 1rad/sec and the viscous modulus G″₃₇ at a frequency of 1 rad/sec is alsodefined for the topical adhesive. This difference gives an indication ofthe behaviour of the topical adhesive with respect to the level ofadhesive residues left on the skin after removal of the topicaladhesive. The adhesive further has a dynamic elastic behaviour definedas ΔG′₃₇ which is the difference of G′₃₇ at a frequency of 100 rad/secand G′₃₇ at a frequency of 1 rad/sec and a dynamic viscous behaviourΔG″₃₇ which is the difference of G″₃₇ at a frequency of 100 rad/sec andG″₃₇ at a frequency of 1 rad/sec.

The topical adhesive according to the present invention satisfies thefollowing conditions:

G′₃₇ (1 rad/sec) is in the range 1500 Pa to 20000 Pa, preferably 1500 Pato 15000 Pa, most preferably 3000 Pa to 10000 Pa.

G″₃₇ (1 rad/sec) is in the range 100 Pa to 15000 Pa, preferably 100 Pato 10000 Pa, most preferably 300 Pa to 5000 Pa.

the ratio of G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the range of 3 to30.

the ratio$\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

 is not less than 0.5, preferably in the range 0.7 to 3, most preferablyin the range 1 to 1.8.

either the ratio of ΔG′₃₇/G′₃₇ (1 rad/sec) is not greater than 1.5,preferably not greater than unity and most preferably not greater than0.8,

or ΔG′₃₇ is not greater than 10000 Pa, preferably less than 5000 Pa,most preferably less than 2000 Pa,

or both.

the difference Δ(G′₃₇−G″₃₇) (1 rad/sec) is greater than or equal to 1250Pa, preferably greater than or equal to 2500 Pa, more preferably greaterthan or equal to 3500 Pa.

Further preferred conditions are:

the value of the ratio G′₃₇/G″₃₇ at least for the frequency range fromabove 1 rad/s up to 100 rad/s should preferably be 3.3 or above, morepreferably 5 or above, most preferably 10 or above, while not exceedingabout 30, preferably 20, anywhere in the frequency interval.

the rheological behaviour can also be related to the values of the GlassTransition Temperature Tg. For topical adhesives according to thepresent invention Tg should preferably be less than −15° C., morepreferably less than −20° C. and most preferably less than −25° C.

the rheological behaviour and acceptance of a topical adhesive can alsobe related to the specific heat capacity. Preferably the specific heatcapacity of the topical adhesive is less than 4 J/g/K, more preferablyless than 3 J/g/K and most preferably less than 2 J/g/K.

the rheological behaviour and acceptance of a topical adhesive can alsobe related to the specific heat conductivity of the adhesive. Preferablythe specific heat conductivity is as low as possible, preferably between1 and 0.1 W/m/K, most preferably between 0.6 and 0.1 W/m/K.

Adhesive compositions which satisfy the above criteria can be used astopical adhesives for functional articles or as components in theformulation of functional articles provided they also satisfy the commonrequirements of being safe for use on human or animal skin during useand generally after disposal of the article.

Often the criteria of hygienic appearance and pleasant feel upon contactare important such that adhesive composition which are transparent orwhite, and which prevent a cold, unpleasant feeling upon application arepreferred.

The above rheological criteria and other considerations can be satisfiedby adhesive compositions where the composition comprises from 45%,preferably from 51%, to 99.5% of a plasticising compound or compositionwhich is liquid at 20° C., from 0.5 to 20%, preferably 5% to 15%, of apolymeric compound or composition which is soluble or swellable in theplasticising compound or composition and with a tackifying resin in anamount in the range from 0% to 50% by weight of the composition,preferably from 0% to 600% by weight of the polymeric compound. Theplasticising compound or composition is preferably selected from thegroup consisting of water, alcohols (preferably glycerol), glycols,polyglycols, liquid polybutenes, oil or combinations thereof. Thepolymeric compound or composition is preferably selected from the groupconsisting of block-copolymer-thermoplastic-elastomers,styrene-block-copolymers and hydrogenated styrene-block-copolymers,polyacrylics, polyvinyl alcohol, natural gum or gelatines,polyethyleneoxide, polyvinylpyrrolidon (PVP), polyvinylethers, cellulosederivatives, or combinations thereof.

DETAILED DESCRIPTION OF THE INVENTION Adhesive for Topical Attachment

The topical adhesive according to the present invention is applieddirectly to the skin. In a particular application the adhesive can beused as a carrier of a function (dispensing of a compound) and forattachment while in other application improvement of the attachment andresistance to rubbing off is desirable. The adhesive according to thepresent invention is used in the context of functional articles such ascosmetic or pharmaceutical delivery articles which provide a substanceto the skin such as skin treatment, substances, creams, lotions,hormones, vitamins, deodorants, or drugs; alternatively cosmetic orpharmaceutical delivery articles can also provide a substance to emanateaway from the skin such as insecticides, inhalation drugs, or perfumes;further the adhesive of the present invention can also be used infunctional articles which are not attached to the skin but as acomponent in articles which require a high residence time on the skinsuch as decorative cosmetics (lipstick, eye colors, stage make-up) orcleaning article (hand cleaner, face mask, hygienic cleanser especiallyfor pores). The word “skin” according to the present invention doesrelate to the outer surface of the derma of humans or animals.

In order to provide fixation of an article according to the presentinvention to the skin it is necessary in some applications to provide acertain area on the side of the article which is facing the skin withthe topical adhesive; the topical adhesive can be provided in a layerhaving a preferred pattern and a thickness or caliper that is preferablyconstant. The layer can be preferably continuous or alternativelydiscontinuous, e.g. in form of dots, spirals, or stripes. In otherapplications the topical adhesive is a compound to the composition ofthe article.

Physical, Rheological and Adhesive Characteristics of a Topical Adhesive

Even though topical adhesives are used like pressure sensitive adhesiveson human skin hair and mucous tissues, it is understood that the topicaladhesive compositions could only with difficulty be considered typicalpressure sensitive adhesives (referred to as PSA hereinafter) on thebasis of the most characteristic rheological behaviours identifying suchmaterials.

In fact as the person skilled in the art of adhesives knows, the mostcharacteristic feature that distinguishes a PSA from other substancesthat can temporarily stick things (as e.g. water between two glassplates could) is the fact that their rheological parameters andespecially the Elastic Modulus G′ vary greatly with the frequency ofapplied stresses. More in particular, G′ of PSA can increase over someorders of magnitude while the frequency of applied stresses varies fromtypical bonding frequency to typical debonding frequency, i.e. 1 rad/sto 100 rad/s as indicated below.

As a first consequence, it derives that it is inadmissible to definematerials intended for use as “topical adhesives” by giving values ofrheological parameters and especially of G′ at a fixed value offrequency. This can be misleading because in the absence of othercharacteristics it will include materials which have no practical value.It is hence necessary that rheological characterisation must be on thebase of dynamic considerations.

This not only applies to the Elastic Modulus G′ but also to the viscousmodulus G″ and hence also for tan (δ)=G″/G′. It is well known thattypical PSA have not only a high variation of G′ across the consideredfrequencies but also there is an even higher variation of G″ which canget close or become even higher than the value of G′, i.e. tan (δ)becomes about or even greater than 1, in particular at the frequenciesthat are typical of the debonding.

Without wishing to be bound by theory this can be interpreted as meaningthat a high fraction of the energy applied for the debonding isdissipated within the adhesive (so it is not effective in causing thedebonding) while this fact causes macroscopically the recording of avery high level of adhesive force.

As indicated above materials useful as topical adhesives according tothe present invention have rheological characteristics which aremeasured at a reference temperature of 37° C. (as usual body temperatureof humans) and in a range of frequencies. It has been found that uponapplication of an article such as a vitamin plaster with a topicaladhesive the adhesive contact is formed at a low frequency, whiledebonding happens at the speed of removing the article. This speed isexpressed as a frequency of 100 rad/s while the low frequency of formingthe adhesive bond has been found to be on the order of 1 rad/s.Therefore, the frequency range for use according to the presentinvention is between 1 and 100 rad/s.

It is believed that the adhesive bonding characteristics are selectedmost appropriately at human body temperature. Since the topical adhesiveaccording to the present invention is used directly on skin and theperson skilled in the art is directed to select the adhesive compositionto have a small specific heat capacity (e.g. preferably less than 4J/g/K) the actual temperature of the topical adhesive will reach 37° C.very quickly or even be warmed up by a human prior to application.

In order to provide good conditions of bonding, i.e. at a frequency ofabout 1 rad/sec, the absolute values of the elastic modulus should notbe too high, otherwise the adhesive is too hard and it is not able tointimately join or mold to the surface to which it is expected toadhere. It is also important to have a low absolute value of G″ in orderto have good cohesion which is particularly valuable when using articleswhich are frequently removed and adhered again or replaced while thematerial remains soft and capable of gently adhering to skin.

The ratio of G′₃₇, (1 rad/sec) over G″₃₇ (1 rad/sec) is important toensure that these two values are balanced upon adhesion to the skin. Atthe same time the absolute changes of G′₃₇ need to be limited within therange of frequencies considered. Hence a value for the ratio of ΔG′₃₇(i.e. G′₃₇ (100 rad/sec)−G′₃₇ (1 rad/sec)) over G′₃₇ (1 rad/sec) has tobe kept small in order to maintain the secure attachment of the topicaladhesive without causing discomfort over time or atremoval/delamination. This can also be expressed in absolute terms bykeeping the ΔG′₃₇ below certain values.

Importantly, the ratio of$\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

needs to be large enough to ensure that the dynamic behaviour of boththe elastic and the viscous module are maintained in a relationshipwhich provides secure adhesion and painless and easy removal.

Further, when considering particularly the removal phase of a topicaladhesive composition for attachment of functional articles to the skinof a wearer, it is commonly recognized that good conditions of removalof the topical adhesive are achieved when the adhesive can be easilyremoved from the skin, and particularly from the hairs that may grow onthe skin where the article contacts the wearer's body, without causingpain to the wearer, therefore without sticking too hard upon removal tothe skin and hairs of the wearer. Particularly, as is apparent to thoseskilled in the art, a good removal also implies that the topicaladhesive does not leave residual remains on the skin or on the hairs.The difference Δ(G′₃₇−G″₃₇) between the elastic modulus G′₃₇ (1 rad/sec)and the viscous modulus G″₃₇ (1 rad/sec) of the topical adhesive of thepresent invention is relevant to the scope of providing a reduced levelof adhesive residues on the wearer's skin after removal of the topicaladhesive. Such a difference gives in fact an indication on the behaviourof the topical adhesive of the present invention as far as the level ofadhesive residues on the skin after removal of the topical adhesive fromthe wearer's skin is concerned.

Without being bound to any theory, it is believed that the differencebetween the elastic modulus G′ and the viscous modulus G″ is a directmeasure of the internal cohesiveness of the topical adhesive. Thereforeincreasing the difference Δ(G′₃₇−G″₃₇), provided the other rheologicalconditions are satisfied, increases the internal cohesiveness of thetopical adhesive, and decreases the possibility that residues ofadhesive remain on the skin upon removal of the topical adhesive.

Finally the person skilled in the art will also recognise that the GlassTransition Temperature Tg of the adhesive composition, specific heatcapacity, and specific heat conductivity are parameters which are usefulto more fully define the group of useful topical adhesives.

The following set of characteristics should be satisfied:

G′₃₇ (1 rad/sec) is in the range 1500 Pa to 20000 Pa, preferably 1500 Pato 15000 Pa, most preferably 3000 Pa to 10000 Pa.

G″₃₇ (1 rad/sec) is in the range 100 Pa to 15000 Pa, preferably 100 Pato 10000 Pa, most preferably 300 Pa to 5000 Pa.

the ratio of G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the range of 3 to30.

the ratio$\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

 is not less than 0.5, preferably in the range 0.7 to 3, most preferablyin the range 1 to 1.8.

either the ratio of ΔG′₃₇/G′₃₇ (1 rad/sec) is not greater than 1.5,preferably not greater than unity and most preferably not greater than0.8,

or ΔG′₃₇ is not greater than 10000 Pa, preferably less than 5000 Pa,most preferably less than 2000 Pa,

or both.

the difference Δ(G′₃₇−G″₃₇) (1 rad/sec) is greater than or equal to 1250Pa, preferably greater than or equal to 2500 Pa, more preferably greaterthan or equal to 3500 Pa.

Further preferred conditions are also:

the value of the ratio G′₃₇/G″₃₇ at least for the frequency range fromabove 1 rad/s up to 100 rad/s should preferably be 3.3 or above, morepreferably 5 or above, most preferably 10 or above, while not exceedingabout 30, preferably 20, anywhere in the frequency interval.

the rheological behaviour can also be related to the values of the GlassTransition Temperature Tg. For topical adhesives according to thepresent invention Tg should preferably be less than −15° C., morepreferably less than −20° C. and most preferably less than −25° C.

the rheological behaviour and acceptance of a topical adhesive can alsobe related to the specific heat capacity. Preferably the specific heatcapacity of the topical adhesive is less than 4 J/g/K, more preferablyless than 3 J/g/K and most preferably less than 2 J/g/K.

the rheological behaviour and acceptance of a topical adhesive can alsobe related to the specific heat conductivity of the adhesive. Preferablythe specific heat conductivity is as low as possible, more preferablebetween 1 and 0.1 W/m/K, most preferably between 0.6 and 0.1 W/m/K.

Chemical and Compositional Characteristics of a Topical Adhesive

In order to provide topical adhesive compositions which satisfy therequirements of the above rheological and physical characteristics of atopical adhesive the following formulation criteria can be used inaddition. It should be noted that the most of the compositions useful astopical adhesive have a substantially gel-like structure and arepreferably gels. This derives from the fact that:

the prevailing component is the plasticiser which is a material liquidat room temperature

a macromolecular or polymeric component is present in minor quantitiesvs. the plasticiser. It forms, in the preferred embodiments, a threedimensional network caused by physical or chemical links between themolecules. Particularly useful physical links are the ones present insystems containing Block Thermoplastic Elastomers.

More specifically, the compositions typically comprise:

from 0.5 to 20%, preferably 5% to 15%, by weight of a macromolecularpolymeric substance or a mixture of such substances soluble or swellablein the below mentioned plasticiser(s). As not limiting examples suchmacromolecular or polymeric substances can be natural and/or syntheticsuch as natural gums or derivatives such as natural gums and gelatins,their derivatives and alginates; polyacrilics; polyvinyl alcohol;polyethylene oxide; polyvinylpyrrolidon (PVP) or polyvinylethers, theircopolymers and derivatives; cellulose derivatives; Block CopolymerThermoplastic Elastomers and preferably Styrenic Block Copolymers andmore preferably the hydrogenated grades Styrol/Ethylene-Butylene/Styrol(SEBS), Styrene/Isoprene/Styrene (SIS), andStyrol/Ethylene-Propylene/Styrol (SEPS).

from 45 to 99.5% by weight, preferably from 51 to 99.5% by weight, of aplasticising substance or a mixture of plasticising substances, whichare liquid at room temperature. As non-limiting examples the plasticisercan be water, various alcohols (like in particular glycerol), glycolsand their ethers, polyglycols, liquid polybutenes, esters suchphthalates, adipates, stearates, palmitates, sebacates, or myristates,natural or synthetic oils such as vegetable oils, mineral oils, orcombinations thereof.

from 0% to 50% by weight of the composition, preferably from 0 to 600%by weight of the macromolecular polymeric substance of a tackifyingresin whose main scope is to tailor the Tg especially in systems basedon synthetic polymers.

from 0 to 10% and more preferably form 0 to 5% by weight of substancesfor facilitating and stabilising the gel and the gel forming processboth of hydrophilic or hydrophobic liquid plasticisers. These may be foroily systems, e.g. the fatty acids of C₈ to C₂₂, their metallic saltsand their polyoxo-derivatives; lanolin derivatives; silica; bentonite,montmorillonite and their derivatives; polyamides, waxes or mixturesthereof.

Common additives known in the art as preservatives, antioxidants, antiUV, pigments, mineral fillers, rheology modifiers etc. can also becomprised in quantities up to 10% each.

When chemical crosslinks are formed in the system, a crosslinking agentcan be present preferably in quantities up to 5% by weight. Chemicalcrosslinking can be formed also by mutual neutralisation of polymershaving different functionalities as in the reaction between acidpolyacrylics and polysaccharides.

The resulting compositions for topical adhesives can be divided intothree families according to the nature of the main component, i.e.usually the liquid plasticiser(s):

1) Hydrophobic compositions in which the plasticiser is typically an oilor blend of oils of vegetable or mineral origin and the polymer isusually a synthetic polymer, preferably an elastomer, soluble orswellable in oil(s).

2) Mixed phase compositions in which both hydrophobic and hydrophiliccomponents, possibly in both plasticisers and polymers, form two or moreseparate phases. In such cases an emulsifier/surfactant is preferablypresent at a suitable level to form stable emulsions between theincompatible phases. For topical adhesives according to the presentinvention it is preferably that the hydrophobic components areprevailing vs. the hydrophilic ones.

3) Hydrophilic compositions in which typically the plasticiser iswater/glycerol/glycols and the like and/or mixtures thereof and thepolymeric phase is of synthetic (e.g. polyacrylics) or natural (e.g.natural gums) origin or mixtures thereof.

It is to stress that, depending on the nature of the functional articlea selection of the family has to take place. For most functionalarticles mixed phases compositions can be preferred. For functionalarticles with a delivery function the compound to be delivered needs tocome out of the topical adhesive composition at different speeds, e.g.perfumes can have a delivery profile which changes from high to lowervalues while drugs have to be delivered preferably at a constant rate toprevent overdosing. Cosmetics often are lipophilic and moisturizing suchthat a combination of watery and oily components can be more desirable.

On the other hand, hydrophilic topical adhesives tend to be perceived ascold and wet which upon application to the skin of a human is not inline with typical expectation. Additional problems result from the factthat in particular topical adhesives comprising water as the plasticiserhave a tendency to dry out unless they are sealed into an impermeablepackage.

Application of Topical Adhesive

Functional articles in which the topical adhesive according to thepresent invention can be used, can be made by any of the ways usual inthe art. The functional article in this context defines whether theadhesive is provided to hold a substrate to the skin or whether theadhesive as part of a composition is directly provided to the skin.

The topical adhesive is preferably protected prior to use. Thisprotection can be provided by a release liner such as a treated paper,providing easy release for the selected topical adhesive or by a closedcontainer in which the functional articles are stored.

If possible, the article also provides breathability by being at leastwater vapour permeable, preferably air permeable to prevent stuffiness.Breathability, if not supported by the topical adhesive as such, can belimited to the area of the article where no adhesive is applied.

In order to evaluate the effect of the difference Δ(G′₃₇−G″₃₇) oftopical adhesives according to the present invention on the amount ofthe adhesive residues that remain on the skin upon removal of thetopical adhesive a Residue Test has been developed. In this test theadhesion of a standard substrate, provided with a layer of topicaladhesives featuring a given value of Δ(G′₃₇−G″₃₇), is achieved on theskin of the forearm of a wearer, and after successive removal the amountof the adhesive residues that remain on the skin is evaluated.

Residue Test

The Residue Test is utilized to evaluate the amount of adhesive residuesthat remain on the wearer's skin after removal of a sample provided witha layer of a topical adhesive and previously attached to the wearer'sforearm skin. The test specifically evaluates the amount of the adhesiveresidues as the residual skin stickiness caused by the adhesiveresidues, in terms of the peak tensile force (N) necessary to detach astandard steel plate adhered to the skin after removal of the samplewith the topical adhesive.

Sample Preparation

The test is performed on rectangular samples 50×20 mm made of apolyester film 23 μm thick, such as that sold by Effegidi S.p.A. ofColorno (Parma, Italy), provided on one side with a continuous layer ofthe selected topical adhesive having a constant thickness of 1.35 mm,applied with an Acumeter Model LH-1 extruder. A release paper is appliedto protect the adhesive layer. The samples are prepared individually andtested after one hour from preparation.

Apparatus

1) Climatically controlled Lab.

Maintenance of 23° C. and 50% Relative Humidity.

2) Instron Limited UK Model 6021 Dynamometer.

Load cell=10N

Test speed=1000 mm/min

3) Weight

1 Kg, cylindrical weight with 44 mm diameter and 82 mm height.

4) Cardboard plate

Square cardboard plate 60×60 mm.

5) Steel plate

Rectangular steel plate 50×60 mm with a smooth flat surface and providedwith means for connection to the movable clamp of the dynamometer.

Residue Measurement

No special treatment of the wearer's skin is required beyond normalcleaning/washing with water and soap and drying at least two hoursbefore the test to allow equilibrium with the room conditions is reachedfor the skin. A rectangular area about 10 mm longer and wider than thedimensions of the sample is selected on the inner part of the wearersforearm skin, e.g. by drawing it on the skin with suitable means, saidarea being centered between the wrist and the elbow, with the long sideof the area aligned with the length of the arm. The sample is thenapplied on the skin by an operator, being centered with respect to thepreviously defined selected area, and a pressure is exerted on it bypositioning by hand the weight on the sample and leaving it there for 30seconds, with the cardboard plate interposed between the weight and thesample in order to cover the whole surface of the sample.

After removal of the weight and of the cardboard plate the sample isworn by the wearer for one hour, and then the sample with the topicaladhesive is removed from the wearer's forearm skin by the operator witha slow and smooth pull, without touching the skin where the sample wasapplied. The steel plate is connected to the upper movable clamp of thedynamometer so that its flat surface is positioned horizontally,perpendicular to the direction of movement of the clamp, and facingdown. The wearer positions his arm horizontally on a suitable supportunder the moving clamp of the dynamometer, with the selected area of theskin where the sample had been applied positioned directly under thesteel plate. The wearer's forearm and the steel plate on the clamp aremutually positioned and oriented in such a way that the steel plate iscentered with respect to the selected area on the forearm, with thelonger dimensions of the steel plate and of the selected area beingparallel, and with the surface of the steel plate and of the forearmskin in the selected area about parallel to each other.

The Instron is operated to move the clamp with the steel plate towardsthe selected area until full contact between the flat surface of thesteel plate and the skin is achieved and to apply a compression force of9.8 N for 30 seconds, then the clamp is raised and the peak tensileforce measured in Newton (N) necessary to detach the steel plate fromthe selected area is recorded as a measure of the residue amount.

The measurements are performed and averaged on five samples of the sametype to ensure a representative residue value to be determined for thesample under investigation.

The amount of adhesive residues left on the skin after removal of thetopical adhesive has been evaluated for two different samples A and Bprovided with two different topical adhesive compositions according tothe present invention.

Sample A and Sample B are provided with a layer of topical adhesiveaccording to Composition 1 and Composition 2, respectively, as describedhereinbelow.

Composition 1

An oil based composition useful on sanitary napkins according to thepresent invention was prepared using 9.9% by weight of Kraton G-1651, aStyrene/Ethylene-Butylene/Styrene block copolymer containing 33% byweight styrene and available from Shell Co., and 59.3% by weight ofKaydol, a paraffinic mineral oil available from Witco Co.

Moreover the composition contained 301 parts of tackifying resin per 100parts of Kraton polymer. The tackifying resin was Escorez 5300, ahydrogenated resin available from Exxon Co.

Magnesium Stearate, available from Carlo Erba S.p.A., was used aco-gelifying agent for oil at a level of 0.7% by weight.

Irganox 1010, an antioxidant available from Ciba-Geigy, was added at alevel of 0.3% by weight.

So finally the formulation had the following percent composition:

Kraton G-1651 9.9% by weight Kaydol 59.3% by weight  Escorez 5300 29.8%by weight  Magnesium Stearate 0.7% by weight Irganox 1010 0.3% by weight

The composition showed the following rheological properties at 37° C.

a) Elastic Modulus at 1 rad/s, G′₃₇=6876 Pa

b) Viscous Modulus at 1 rad/s, G″₃₇=550,5 Pa

c) Ratio of Elastic and Viscous Modulus at 1 rad/s, G′₃₇/G″₃₇=12.49

d) Ratio of$\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}} = 1.22$

e) The ratio of ΔG′₃₇ over G′₃₇ (1 rad/s) was 0.308, with ΔG′₃₇=2124 Pa.

Composition 2

The topical adhesive is an oil based composition containing 10% byweight of Kraton G-1651, a Styrene/Ethylene-Butylene/Styrene blockcopolymer available from Shell Co., 49% by weight of Kaydol, aparaffinic mineral oil available from Witco Co., 40% by weight ofEscorez 5300, a hydrogenated tackifying resin available from Exxon Co.,0.7% by weight of Magnesium Stearate, a co-gelifying agent for oilavailable from Carlo Erba S.p.A., and 0.3% by weight of Irganox 1010, anantioxidant available from Ciba-Geigy.

So finally the formulation had the following percent composition:

Kraton G-1651 10.0% by weight Kaydol 49.0% by weight Excorez 5300 40.0%by weight Magnesium Stearate  0.7% by weight Irganox 1010  0.3% byweight

The composition has the following rheological properties at 37° C.

a) Elastic Modulus at 1 rad/s, G′₃₇=7038 Pa

b) Viscous Modulus at 1 rad/s, G″₃₇ =487 Pa

c) Ratio of Elastic and Viscous Modulus at 1 rad/s, G′₃₇/G″₃₇=14.45

d) Ratio of$\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}} = 1.11$

e) The ratio of ΔG′₃₇ over G′₃₇ (1 rad/s) was 0.291, with ΔG′₃₇ =2051Pa.

The results of the test are summarized in the following table:

Sample Δ(G′₃₇-G″₃₇) (Pa) Residue (N) A 6326 0.33 B 6551 0.27

The results show that increasing values of the difference Δ(G′₃₇−G″₃₇)correspond to lower amounts of adhesive residues left on the wearer'sskin after removal of topical adhesive compositions according to thepresent invention.

Moreover, the above described topical adhesive compositions according tothe present invention have been judged as comfortable for initialapplication and for removal form sensitive, hairy skin without causingpain.

What is claimed is:
 1. A topical adhesive for application of functional articles to the skin, said functional articles being cosmetic or pharmaceutical delivery articles, decorative cosmetics or cleaning articles, said adhesive having an elastic modulus at a temperature of 37° C. (100° F.), G′₃₇, a viscous modulus at a temperature of 37° C. (100° F.), G″37, and a difference Δ(G′₃₇−G″₃₇) between said elastic modulus G′₃₇ (1 rad/sec) and said viscous modulus G″₃₇, said adhesive being selected to have G′₃₇ (1 rad/sec) in the range 1500 Pa to 20000 Pa; G″₃₇ (1 rad/sec) in the range 100 Pa to 15000 Pa; the ratio G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the rage 3 to 30; the radio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

is not less than 0.5; alternatively either G′₃₇ (100 rad/sec)−G′₃₇ (1 rad/sec) is not greater than 10000 Pa; or the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}}{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}$

is not greater than 1.5, or a combination thereof, the difference Δ(G′₃₇ 31 G″₃₇) (1 rad/sec) is greater than or equal to 1250 Pa; said topical adhesive comprising: from 45% to 99.5% by weight of a hydrophobic plasticizing compound or composition which is liquid at 20° C.; from 0.5% to 20% by weight of a polymeric compound or composition which is solvable or swellable in said plasticizing compound or composition; a tackifying resin in an amount of from 0% to 50% by weight of said composition.
 2. A topical adhesive according to claim 1, wherein said adhesive is provided as a continuous layer.
 3. A topical adhesive according to claim 1 wherein said plasticising compound or composition is selected from the group consisting of mineral oil, vegetable oil, or other oil and combinations thereof; and said polymeric compound or composition is selected from the group consisting of block-copolymer-thermoplastic-elastomers, styrene-block-copolymers and hydrogenated styrene-block-copolymers.
 4. A functional article suitable for use as a cosmetic or pharmaceutical delivery article, a decorative cosmetic or a cleaning article, said functional article comprising a topical adhesive according to claim 1 for application of said functional article to the skin.
 5. The method of using a topical adhesive according to claim 1 for application of functional articles to the skin, said functional articles being cosmetic or pharmaceutical delivery articles, decorative cosmetics or cleaning articles.
 6. A topical adhesive according to claim 1 wherein: said adhesive being selected to have G′₃₇ (1 rad/sec) in the range 1500 Pa to 15000 Pa, G″₃₇ (1 rad/sec) in the range 100 Pa to 10000 Pa the ratio G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the range 3 to 30; the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

is in the range 0.7 to 3, alternatively either G′₃₇ (100 rad/sec)−G′₃₇ (1 rad/sec) is not greater than 5000 Pa, or the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}}{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}$

is not greater than 1, or a combination thereof, the difference Δ(G′₃₇−G″₃₇) (1 rad/sec) is greater than or equal to 2500 Pa.
 7. A topical adhesive according to claim 1 wherein: said adhesive being selected to have G′₃₇(1 rad/sec) in the range 3000 Pa to 10000 Pa; G″₃₇ (1 rad/sec) in the range 300 Pa to 5000 Pa; the ratio G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the range 3 to 30; the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

is in the range 1 to 1.8; alternatively either G′₃₇ (100 rad/sec)−G′₃₇ (1 rad/sec) is not greater than 2000 Pa; or the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}}{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}$

is not greater than 0.8, or a combination thereof, the difference Δ(G′₃₇−G″₃₇) (1 rad/sec) is greater than or equal to 3500 Pa.
 8. A topical adhesive according to claim 1 comprising from 51% to 99.5%, by weight of a plasticising compound or composition which is liquid at 20° C.; from 0.5% to 20% by weight of a polymeric compound or composition which is solvable or swellable in said plasticising compound or composition; a tackifying resin in an amount of from 0% to 600% by weight of said polymeric compound.
 9. A cosmetic, pharmaceutical, decorative cosmetic or cleaning article delivery system comprising: a substrate; a substance; and, a hydrophobic adhesive for application of said delivery article to the skin; said adhesive having an elastic modulus at a temperature of 37° C. (100° F.), G′₃₇, a viscous modulus at a temperature of 37° C. (100° F.), G″₃₇, and a difference Δ(G′₃₇−G″₃₇) between said elastic modulus G′₃₇ (1 rad/sec) and said viscous modulus G″₃₇, said adhesive being selected to have G′₃₇ (1 rad/sec) in the range 1500 Pa to 20000 Pa; G″₃₇ (1 rad/sec) in the range 100 Pa to 15000 Pa; the ratio G′₃₇ (1 rad/sec)/G″₃₇ (1 rad/sec) is in the range 3 to 30; the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {100\quad {{rad}/\sec}} \right)}}{{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)} - {G_{37}^{''}\left( {1\quad {{rad}/\sec}} \right)}}$

is not less than 3; alternatively either G′₃₇ (100 rad/sec)−G′₃₇ (1 rad/sec) is not greater than 10000 Pa; or the ratio $\frac{{G_{37}^{\prime}\left( {100\quad {{rad}/\sec}} \right)} - {G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}}{G_{37}^{\prime}\left( {1\quad {{rad}/\sec}} \right)}$

is not greater than 1.5, or a combination thereof, the difference Δ(G′₃₇−G″₃₇) (1 rad/sec) is greater than or equal to 1250 Pa.
 10. A delivery system as claimed in claim 9 wherein said adhesive is protected prior to use, wherein said protection is selected from the group consisting of a treated paper release liner and a closed container.
 11. A delivery system as claimed in claim 9 wherein said substance is selected from the group comprising skin treatment substances, creams, lotions, hormones, vitamins, deodorants, drugs, decorative cosmetics and cleaning articles.
 12. A delivery system as claimed in claim 9 wherein said delivery article further comprises a substance that emanates outwardly from the skin.
 13. A delivery system as claimed in claim 12 wherein said outwardly emanating substance is selected from the group comprising insecticides, inhalation drugs and perfumes.
 14. A delivery system as claimed in claim 9 wherein said delivery article provides breathability by being water vapor permeable.
 15. A delivery system as claimed in claim 9 wherein said delivery article is permeable to air.
 16. A delivery system as claimed in claim 9 wherein said said topical adhesive comprises: from 45% to 99.5% by weight of a hydrophobic plasticizing compound or composition which is liquid at 20° C.; from 0.5% to 20% by weight of a polymeric compound or composition which is solvable or swellable in said plasticizing compound or composition; a tackifying resin in an amount of from 0% to 50% by weight of said composition.
 17. A delivery system as claimed in claim 16 wherein said plasticizing compound or composition is selected from the group consisting of, mineral oil, vegetable, other oil and combinations thereof.
 18. A delivery system as claimed in claim 16 wherein said polymeric compound or composition is selected from the group consisting of block-copolymer-thermoplastic-elastomers, styrene-block-copolymers and hydrogenated styrene-block-copolymers. 